(HealthDay News) -- Chronic cough is one that persists for longer than three weeks. The cough may be caused by an illness, a behavior such as smoking, or as a side effect of a medication.

Here are common reasons for chronic cough, courtesy of the American Academy of Family Physicians:

• Smoking.
• Asthma.
• Medications, including ACE inhibitors used to treat high blood pressure, or beta blockers used to treat high blood pressure, glaucoma or migraines.
• Acid reflux (heartburn), when the acid in your stomach backs up into your throat.
• Allergies, which can trigger cough-inducing postnasal drip.